1. Field of the Invention
The present invention relates to purging of containers accommodating semiconductor wafers or other articles, for example.
2. Description of the Related Art
In semiconductor factories, cassettes for accommodating semiconductor wafers are transferred by an overhead transfer system between load ports of processing equipment. Japanese Patent Document 5229363 discloses, as a temporary buffer between the overhead transfer system and the load ports, an apparatus including a local vehicle, its travelling rail, and a buffer between the load ports and the travelling rail for the overhead transfer vehicles. In the apparatus disclosed in Japanese Patent Document 5229363B, the cassettes may vertically pass through a gap between a pair of travelling rails for the local vehicle, and the buffer under the travelling rails for the local vehicle allows both the overhead transfer vehicles and the local vehicle to access.
In addition, stockers for storing the cassettes having a purging function to purge the cassettes by nitrogen (N2) gas, etc., have been known. However, in other places than the stocker, purging is not possible.
When containers are purged with N2 and so on during transfer from one piece of processing equipment to the next piece of processing equipment, then, problems such as oxidation of the wafer surface are reduced. The purge increases the allowance time for the transfer to the next piece of processing equipment. However, it is not realistic to provide a purging apparatus within processing equipment, since it needs a large-scale remodeling of processing equipment. Therefore, a purging apparatus is necessary in the vicinity of processing equipment.